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Версия для печати | Главная > Центр > Научные советы > Научный совет по катализу > ... > 2025 год > № 113

№ 113

 

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  • V Российский конгресс по катализу «РОСКАТАЛИЗ»
  • К 100-летию введения концепции «активных центров в катализе». В.А. Лихолобов
  • Международная конференция «Динамические процессы в каталитических структурах»
  • Защита диссертаций в области катализа
  • За рубежом
  • Приглашения на конференции



V Российский конгресс по катализу «РОСКАТАЛИЗ»

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К 100-летию введения концепции «активных центров в катализе»

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Международная конференция «Динамические процессы в каталитических структурах»

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Защита диссертаций в области катализа

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A simpler way to make complex piperidines

Route combines biocatalytic oxidation and radical cross-coupling

A new, two-step strategy for making substituted piperidines offers chemists a more efficient way to make these biologically relevant molecules. The method, which leverages enzymatic oxidation and radical cross-coupling, helps medicinal chemists quickly access structures that feature piperidine. It also sidesteps many reactions that require precious metal catalysts or expensive chiral ligands, thus making the route appealing to process chemists.

Nitrogen-containing aromatic rings like pyridine have long been popular motifs to include in drug candidates. But drugmakers looking to escape the aromatic flatlands by making molecules that reach into three dimensions have been eyeing piperidine—the unsaturated version of pyridine—as an alternative motif. The problem is that while there is well-established chemistry for adding various groups onto pyridines, there hasn’t been a convenient strategy for adding substituents to piperidines—until now.

“We thought that the combination of enzymatic functionalization and radical coupling could be leveraged to do something groundbreaking,” says Yu Kawamata of Scripps Research, who led the project along with Scripps colleague Phil S. Baran and Hans Renata at Rice University.

“Looking at various piperidines that are present in drug molecules, you see all kinds of substitution patterns,” Renata says. The diversity of arrangements didn’t point to an obvious general strategy. But the approach becomes clear if one considers using radical cross-coupling to make a carbon-carbon bond from a hydroxy group and works backward from there, he says.

The chemists started with commercially available enantiopure 2- and 3-carboxylated piperidines. Using directed evolution, they developed a series of enzymes that selectively oxidize a variety of C–H bonds on the piperidine, which provides access to a series of carboxylated piperidines with hydroxy handles. They then used radical cross-coupling reactions to forge C–C bonds on the piperidines at the sites of those hydroxy handles. Those compounds are intermediates en route to complex substituted piperidines, including the neurokinin 1 antagonist (+)-L-733,060 (shown) and the natural product swainsonine (Science 2024, DOI: 10.1126/science.adr9368).

Frank Lovering, a consultant with Thames Pharma Partners who has advocated for making more drug candidates with saturated motifs, says that using enzymes to direct functionalization of the piperidine at specific points around the ring gives chemists access to multiple molecules of interest. “However, these enzymes will need to be commercially available for this approach to be viable in the medicinal chemistry setting,” he says in an email, and currently they are not.

L.-C. Campeau, head of small-molecule process chemistry at Merck & Co., says the reaction combination demonstrates a way to eliminate inefficient steps on the way to key building blocks. “This is the type of strategy that can significantly streamline routes and enable a more green and sustainable future for chemical synthesis,” he says in an email.

 

A simple solution to a chlorination challenge

Iron-catalyzed reaction functionalizes less-favored positions with less fuss


Two consecutive anti-Markovnikov hydrochlorinations of an alkyne, via the West group’s iron-catalyzed method.
Using heavy water in the second step, the researchers incorporated a deuterium atom into the product.

One of the first reactions that students learn in college-level organic chemistry is hydrochlorination—adding hydrogen chloride to a carbon-carbon double or triple bond. The classic textbook version preferentially installs the chlorine atom on the more substituted carbon in the bond, according to a selectivity principle known as the Markovnikov rule. Sticking the chlorine to the less substituted carbon is a much trickier proposition.

Traditionally, chemists have had to resort to harsh conditions, pricey reagents, or multiple synthetic steps to manage anti-Markovnikov hydrochlorination. But Julian West and his team at Rice University have devised a new way to do it with inexpensive catalysts and mild conditions (Nat. Synth. 2025, DOI: 10.1038/s44160-024-00698-z).

West says he and his group had been looking for ways to extend the iron-based radical photocatalyst system they had developed for attaching fluorinated groups to double bonds. They realized that if they used their system to generate chlorine radicals, they could do hydrochlorina-tion chemistry with flipped selectivity.

“It’s really selective for a wide range of alkenes and alkynes, but it’s also really easy to set up,” says West. Because the new approach uses inner-sphere electron transfer to generate the radicals and a thiophenol cocatalyst to shuttle hydrogen atoms, it is compatible with molecules that are easily oxidized or sensitive to ac-id—which other methods often are not. The researchers also found that doubly hydrochlorinating a triple bond with this reaction gives a product with each chlorine bound to a different carbon atom, whereas the classic method would stick them both on the same carbon.

Using heavy water, the researchers could also selectively introduce deuterium atoms along with chlorine. The weightier hydrogen isotope is useful for probing reaction mechanisms, as well as studying and tuning drugs’ metabolic stability.

To showcase the reaction’s versatility and selectivity for installing chlorine, hydrogen, and deuterium atoms in previously hard-to-access positions on molecules, the researchers reported 125 molecules made with the new chemistry, including derivatives of drugs and natural products.

Elias Picazo, an organic chemist at the University of Southern California who was not involved in the work, says it’s “definitely a synthetic advance” in terms of its scope and selectivity. He thinks that the commercially available iron catalyst will be appealing to chemists in both academia and industry.

West says he and his group aim to develop chemistry that people will find useful and approachable. The goal, he says, is to make reactions where “If somebody likes them, they could try them the same day.”

Chemical & Engineering News


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